Thermal Performance of Exposed Composed Roofs in Very Hot Dry Desert Region in Egypt (Toshky)

Abstract

Thermal performance for any building in hot dry region depend on the external climatic factor, the ability of the construction materials used in gained heat through day time and loss this heat through night time through the nocturnal radiation. Roof is considered the major part of the building envelop which exposed to high thermal load due to the high solar intensity and high outdoor air temperature through summer season which reach to 6 months. In Egypt the thermal effect of roof is increased as one go towards from north to south. This study evaluate the thermal performance of different test rooms with different roofs construction; uninsulated concrete, insulated concrete, double, plant, and active concrete roofs, constructed under the effect of external climatic condition of very hot and dry region in Egypt (Toshky region). The external climatic conditions and the temperature distribution inside the roof construction and the indoor air temperature were measured. The results of this study recognized that the thermal transmittance (UValue) has a major role in chosen the constructed materials. Also the thermal insulation considered the suitable manner for damping the thermal stresses through day time and makes the interior environment of the building near the comfort zone during most months of the year. Natural night and forced ventilation are more important in improving the internal conditions. The construction roof systems show that the indoor air temperature thermal damping reach to 96%, 90%, 89%, and 76% for insulated concrete, double, planted and uninsulated concrete roofs. The results also investigate the importance of using the earth as a cooling source through the active concrete system. Evaporative cooling and movable shading which are an integrated part of the guidelines for building design in hot dry region must be using.